The present invention concerns a novel restriction device for a strapping machine which prevents strapping material, which has either failed to feed or which has broken, from becoming loose and falling into the slack box of a strapping machine.
Strapping machines comprise a number of elements that allow for a strap to be fed from a reel to a strapping head and then onto an object to be strapped. Within the strapping machine the strapping material must be fed through a number of elements that allow the strapping material to travel quickly, efficiently, and accurately towards an object to be strapped. In the operation of strapping machines the strap is first propelled in a forward direction towards the item to be strapped and then the strap is pulled around the item and tightened. Means are provided to reverse the direction of strap travel so that strap may be tightened about the object prior to cutting the strap and so that cutting and securing strap can be accomplished with little waste of material. Strap pulled back into the machine during the tightening process is subsequently released, within the strap path, for further strapping. However, because strap can double up when released, which may result in a restriction of its movement, use of these complex strapping machines is often times impeded by a blockage of loose strap.
Because of the nature of the strapping material, and the need for the material to move rapidly through the strapping machine, no single element of these machines generally holds the loose end of the strapping material within the strapping machine. In some present strapping machines, upon the breaking of an end of the strapping material, the leading end of the strap which is left in the strapping machine is subjected to the pull of gravity and inertia during take-up and little, if any, restraint. The strap end, therefore, often falls or coasts from the guiding members of the machine into the slack box of the machine. This action is known as xe2x80x9csuck-backxe2x80x9d by users of strapping machines. When suck-back occurs, the end of the reel must be retrieved and the strapping machine must be re-threaded. This process is time consuming and causes delays in the strapping process.
Previously, a fixed type of restrictor has been tried in certain strapping machines. The fixed restrictors, which have been placed between the strap gate and the winder (or strap tensioning device) have proven to be effective in preventing suck back, but also simultaneously restrict strap, which is not broken or loose, from proceeding in the strap path after certain normal machine operations. For example, after an unwinding (a common event in a strapping cycle), strap may form a xe2x80x9ctear dropxe2x80x9d shaped loop. In a machine with a fixed restrictor, strap material in the shape of a tear drop may be prevented from passing through the fixed restrictor because of the inherent doubling up of the thickness of the strap in such a loop. Further, a fixed restrictor may prevent loops of strap from pulling out of the slack box and into the head, for similar reasons.
In accordance with the present invention, a strapping machine, having a strap restriction device, a winder, a strap gate, and a slack box is provided. The strap restriction device is provided with an upper guide, having a first end and a second end and a lower guide, having a first end and a second end, said first end of said lower guide being rotationally connected to said first end of said upper guide. The upper guide and the lower guide are biased apart by a spring which urges the second end of the upper guide apart from the second end of the lower guide. In a first default position, the second end of the upper guide is generally disposed, by the spring, toward the winder and the second end of the lower guide is generally disposed toward the strap gate. In the first default position, the upper and lower guides form a strapping guide between the winder and the strap gate and restrict the size of the path for the strapping material. Further, the ends of the upper and lower guide in the first default position, together, form a strap path which provides a frictional surface on which the strap may drag. In these ways the restriction device prevents strapping material from falling or coasting into the slack box.
As the guides are spring biased the movement of strap, respectively, beneath or above the lower and upper guide, can change the position of the guides depending on the tension and force applied to the guides by the strap. The lower guide, when forced upward by strap, provides less of a restriction for the strap to travel through allowing for quicker strap speeds. When the upper guide is forced downward by strap, the restriction device provides less restriction below the winder, allowing quicker clean up of looped material. For example, the formation of a loop of material, due to any number of causes, including the winding and subsequent unwinding of strapping material, may cause the upper guide to be forced downward. When the upper guide is forced downward less restriction occurs for strap passage between the guide and the winder, allowing the loop of strap to be more quickly pulled out of the machine. Similarly, a loop between the lower guide and the strap gate is more quickly removed when the guide is forced upward by the strap.
In one embodiment of the present invention the lower guide is divided into two sections along its longitudinal axis and the upper guide is rotationally set between the two section of the lower guide and attached to a strapping machine. The lower guide sections and the upper guide are biased apart at their second ends by a spring such that the upper guide is disposed upward and the two sections of the lower guide are disposed downward. In this manner strap which may travel laterally along the strapping gate, may be more easily guided by the two separate parts of the lower guide.
A more detailed explanation of the invention is provided in the following description and claims and is illustrated in the accompanying drawings.